Update package.json to CRA2 and cleanup React Component imports

[js-mode]

Updated all of the package.json files to include proper exercise number in the name.

Updated all of the package.json files to include latest version of Create React App. Tested locally and yarn install works, but when one runs yarn install it will ask for the default browser to be added to the package.json automatically.

Also cleaned up the import React, { Component } from 'react'; statement so it is consistent throughout all of the exercises.

Added a few minor changes to make the event parameter more descriptive so it was event instead of e.

[js-mode]

I just pulled down all of the latest changes from the master branch to make sure nothing was overwritten and the new App.solution.js file for Exercise 04 should be the latest version.